“ It is settled by the decisions of the supreme court of Illinois that an oil and gas lease like that of the complainants passes to the lessee, his heirs and assigns, a present vested right-'a freehold interest'-in the premises, that this interest is taxable as real property, and that the clause giving the lessee an option to surrender the lease at any time is valid, does not create a tenancy at will or give the lessor an option to compel a surrender, and does not make the lease void as wanting in mutuality. ”

“ As respects the cost incurred prior to August 1, 1907, we think the objection is well taken, for up to that time Solley and his associates were in actual ignorance of the earlier lease, and were proceeding in the honest belief that the later lease, assigned to them by Willett, was the only one upon the premises. They paid a substantial sum for it, were let into possession by the lessor, and were not conscious that they were invading the rights of others. ”

“ This was a suit in equity, brought in the circuit court of the United States for the eastern district of Illinois, by the holders of an oil and gas lease covering a small tract of land in Crawford county, Illinois, to enjoin operations under a later and similar lease, and to obtain a discovery and an accounting in respect of the oil and gas produced and sold in the course of operations already had. ”